And what is the output of nmap? Can you add it to your question?
–
jaumeNov 14 '12 at 10:15

2

And what does netstat -an | grep 49176 say? (Run it also inside Terminal on your Mac.)
–
jaumeNov 14 '12 at 10:35

1

Next time this happens, run lsof -i -P | grep <port> on the Mac, you will see the application that binds to that port. If the Mac's firewall is active it must be one of the applications listed in System Preferences>Security & Privacy>Firewall with comment Allow incoming connections.
–
jaumeNov 14 '12 at 14:53